FORTUNE -- Using some pixel math and Photoshop work, Marco ("Instapaper") Arment generated the image above, which adds to Apple's current mobile lineup -- the iPhone 5, iPad mini and iPad -- a device he calls the iPhone plus.
The new device would be a response to Samsung's Galaxy Note -- a "phablet" with a 5.3-inch screen that has been selling surprisingly well, especially overseas, despite its awkward size.
"The iPhone has lost a significant number of sales by buyers either wanting a larger screen or being drawn to how much better the large screens look in stores," Arment wrote Thursday on his Marco.org blog. To make his point he shows how Apple's (AAPL) theoretical iPhone Plus would look next to the large-screened competition:
"Now, imagine that lineup without the iPhone Plus mockup," he suggests. "That's how the shelf looks today when a buyer goes into a phone store. See the problem?"
Arment lays out his argument, with detailed screen specs, in A crazier prediction: iPhone Plus is real, and huge.
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